Thank you both. I finally had figured out which tree of the two possibilities was the Sacred Tree, actually it had made sense, but the entire time I was looking around the tree there was nothing that in any way indicated ANYTHING. This is because I insisted on actually clicking on the tree itself. Finally, in desperation, I clicked on the corner of the Peteran Monastery closest to the tree and voila, the symbol changed from an arrow to a leaf. I knew at that point I had found the tree and then I just went around and clicked on various plants etc. till the correct message showed up.
The key to this quest is look at it as if it is a mass of rabbit holes. You will never actually see the items you are searching for. You also have two choices as to how you should search, by the list of items, or by the locations the monarch had gone to. Only one is at all helpful or easy. I've done it both ways and my second attempt was much easier until I hit the tree!